UNIVERSITY  OF  CAFIFOBNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


The  Preparation  of  Nicotine 
Dust  as  an  Insecticide 


BY 

RALPH   E.   SMITH 


BULLETIN  No.  336 

November,  1921 


UNIVERSITY  OF  CALIFORNIA  PRESS 

BERKELEY 

1921 


David  P.  Barrows,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 

HEADS   OF  DIVISIONS 

Thomas  Forsyth  Hunt,  Dean. 

Edward  J.  Wickson,  Horticulture  (Emeritus). 

,  Director  of  Resident  Instruction 

C.  M.  Haring,  Veterinary  Science,  Director  of  Agricultural  Experiment  Station. 

B.  H.  Crocheron,  Director  of  Agricultural  Extension. 

James   T.   Barrett,   Plant   Pathology;    Acting   Director   of   Citrus   Experiment 
Station. 

Hubert  E.  Van  Norman,  Dairy  Management. 

William  A.  Setchell,  Botany. 

Myer  E.  Jaffa,  Nutrition. 

Ralph  E.  Smith,  Plant  Pathology. 

John  W.  Gilmore,  Agronomy. 

Charles  F.  Shaw,  Soil  Technology. 

John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 

Frederic  T.  Bioletti,  Viticulture  and  Fruit  Products. 

Warren  T.  Clarke,  Agricultural  Extension. 

Ernest  B.  Babcock,  Genetics. 

Gordon  H.  True,  Animal  Husbandry. 

Walter  Mulford,  Forestry. 

Fritz  W.  Woll,  Animal  Nutrition. 

W.  P.  Kelley,  Agricultural  Chemistry. 

H.  J.  Quayle,  Entomology. 

Elwood  Mead,  Rural  Institutions. 

H.  S.  Reed,  Plant  Physiology. 

L.  D.  Batchelor,  Orchard  Management. 

J.  C.  Whitten,  Pomology. 

fFRANK  Adams,  Irrigation  Investigations. 

C.  L.  Roadhouse,  Dairy  Industry. 

E.  L.  Adams,  Farm  Management. 

W.  B.  Herms,  Entomology  and  Parasitology. 

F.  L.  Griffin,  Agricultural  Education. 
John  E.  Dougherty,  Poultry  Husbandry. 

D.  R.  Hoagland,  Plant  Nutrition. 

G.  H.  Hart,  Veterinary  Science. 

L.  J.  Fletcher,  Agricultural  Engineering. 
Edwin  C.  Voorhies,  Assistant  to  the  Dean. 

division  of  plant  pathology 

R.  E.  Smith  E.  H.  Smith 

W.  G.  Horne  B.  A.  Rudolph 


*  In  cooperation  with  office  of  Public  Roads  and  Rural  Engineering,   U.  S.  Department  of 
Agriculture. 


THE  PREPARATION  OF  NICOTINE  DUST 

AS  AN  INSECTICIDE 

By  EALPH  E.  SMITH 


The  idea  of  a  standardized  nicotine  dust,  first  suggested  by  the 
writer  as  an  improvement  on  tobacco  dust  for  the  control  of  the  walnut 
aphis,  has  aroused  much  interest  in  connection  with  the  possibilities 
of  destroying  a  number  of  other  insect  pests  by  dusting  where  liquid 
spraying  is,  for  one  reason  or  another,  ineffective  or  impractical. 
Several  other  kinds  of  aphis,  various  leaf  hoppers  and  thrips  and  a 
number  of  lepidopterous  larvae,  beetles  and  bugs  are  already  being 
successfully  combatted  by  this  means,  and  it  is  believed  that  important 
possibilities  have  been  opened  for  further  development. 

The  present  publication  has  been  prepared  in  order  to  make  known 
the  methods  and  results  of  the  work  thus  far. 

HISTORICAL 

The  indisputable  advantages  of  the  dusting  method  of  applying 
insecticides  and  fungicides  have,  to  a  considerable  extent,  been  offset 
by  a  lack  of  materials  adapted  to  this  method  of  application.  The 
writer  was  attracted  to  dusting  in  an  effort  to  find  means  of  combat- 
ting the  Walnut  Blight,  a  bacterial  infection  (Pseudomonas  juglandis 
Pierce)  which  annually  causes  great  losses  in  California.  In  spite 
of  many  efforts,  and  the  occurrence  of  a  number  of  serious  pests,  the 
spraying  of  walnut  trees  with  liquid  materials  has  never  become 
common  on  account  of  the  large  size  of  the  trees,  which  makes  spraying 
laborious,  costly  and  slow,  even  though  not  impossible. 

The  effort  of  the  writer  to  control  Walnut  Blight  by  dusting 
consisted  mainly  in  the  application  of  sulphur.  This  did  not  control 
the  disease  but  rather  caused  considerable  injury  to  the  trees  by  sul- 
phur burning  during  periods  of  hot  weather.  On  account  of  the 
prevalence  of  the  walnut  aphis  (Chromaphis  juglandicola  Kalt.)  along 
with  the  blight,  an  effort  was  made  to  control  this  insect  by  dusting 
at  the  same  application  and  this  has  resulted  in  a  success  which  has 
quite  overshadowed  the  original  idea  of  controlling  the  walnut  blight. 

The  first  experiments  were  made  in  May  and  June,  1917.  A  power 
blower  was  purchased  from  the  Niagara  Sprayer  Co.,  of  Middleport, 
N.  Y.,  together  with  a  supply  of  superfine  (ground)  dusting  sulphur, 
mixed  with  tobacco  dust  in  the  proportion  of  50-50.  This  tobacco 
contained  about  1%  nicotine.  Applications  were  made  at  Goleta 
(near  Santa  Barbara),  Santa  Paula,  El  Monte  and  Santa  Ana,  using 


262  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

from  3  to  5  pounds  of  dust  per  tree.  Walnut  dusting  was  also  done  at 
San  Jose,  using  in  this  case  pure  tobacco  dust.  Some  work  was  also 
done  with  a  50-50  mixture  of  tobacco  dust  and  hydrated  lime. 

In  all  this  work  the  results  on  aphis  were  excellent.  Not  only  were 
the  trees  which  were  actually  dusted  cleaned  of  the  pest,  but  usually 
the  trees  for  at  least  three  rows  to  the  windward  of  the  last  row  dusted 
were  equally  well  "de-loused."  Wherever  sulphur  was  used,  how- 
ever, the  unprecedented  heat  wave  of  June  15-20,  1917,  caused  great 
injury. 

Encouraged  by  this  success  in  aphis  control,  a  number  of  walnut 
growers  ordered  power  dusters  and  a  large  quantity  of  tobacco  dust 
for  the  season  of  1918.  This  tobacco  was  mixed  50-50  with  hydrated 
lime  or  kaolin,  rather  than  with  sulphur.  In  the  spring  of  1918 
dusting  was  started  on  quite  an  extensive  scale,  but  the  results  were 
disappointing  and  very  different  from  those  obtained  in  1917.  Inves- 
tigation soon  showed  that  the  tobacco  dust  which  had  been  purchased 
had  very  little  effect  upon  aphis  and  upon  analysis  it  was  found  to 
contain  only  a  small  fraction  of  1  per  cent  of  nicotine. 

As  a  result  of  this  failure  work  was  begun  upon  an  idea  which  had 
been  growing  ever  since  the  tobacco  dusting  commenced.  This  idea 
was  that  of  making  an  artificial  nicotine-containing  dust  in  order  to 
obtain  a  definite,  standard  strength  and  also  to  get,  if  needed,  a  dust 
containing  more  nicotine  than  any  ordinary  tobacco  dust.  The  plan 
in  a  general  way,  was  to  mix  a  definite  amount  of  nicotine  with  an 
inert  carrier  or  filler  and  reduce  the  product  to  a  dry,  uniform, 
extremely  fine  powder  or  dust.  As  a  source  of  nicotine  the  commercial 
preparation  called  "Black  Leaf  40"  was  the  most  available  material. 
This  is  a  concentrated  liquid  extract  of  waste  tobacco,  guaranteed  to 
contain  40  per  cent  of  nicotine  in  the  form  of  nicotine  sulphate.  The 
carrier  used  was  a  fine  grade  of  kaolin  obtained  from  lone,  California.1 

The  first  dust  made  in  any  considerable  amount  was  mixed  by  hand 
in  sheet-iron  pans  about  six  inches  deep,  each  holding  100  pounds 
of  material.  The  required  amount  of  "Black  Leaf  40"  was  diluted 
with  enough  water  to  make  a  stiff  mud  with  the  kaolin.  This  was 
thoroughly  mixed,  air-dried  (requiring  several  days),  and  then  pul- 
verized by  some  convenient  means  of  breaking  up  the  soft  lumps. 
Material  made  in  this  way  was  used  for  determining  the  strength 
necessary  to  kill  different  kinds  of  aphids.  Strengths  ranging  from 
1  per  cent  to  10  per  cent  of  "Black  Leaf  40"  by  weight  (.4  per  cent 
to  4  per  cent  nicotine)  appeared  to  be  required  for  different  species. 
Credit  is  due  to  Mr.  F.  A.  Frazier  of  Berkeley  for  suggestions  and 
assistance  at  this  point  in  the  work. 


Bulletin  336]  NICOTINE  DUST  AS  AN  INSECTICIDE  263 

At  this  time  the  name  Nicodust  was  suggested  by  the  writer 
and  this  term  has  come  into  quite  general  use  to  designate  nicotine- 
containing  dust  mixtures.  Nicosulphur  is  also  a  convenient  name  for 
the  combination  which  it  suggests.* 

The  possibility  of  controlling  the  walnut  aphis  with  nicodust  led, 
at  this  point,  to  cooperative  arrangements  between  the  Agricultural 
Experiment  Station  of  the  University  of  California  and  the  California 
Walnut  Growers'  Association.  Work  was  commenced  at  Los  Angeles, 
where  several  tons  of  dust  was  made  during  the  summer  of  1918.  The 
method  here  consisted  in  placing  the  kaolin  in  the  large  pans  pre- 
viously described  and  sprinkling  over  it  the  proper  amount  of  ' '  Black 
Leaf  40,'  (2  per  cent  for  walnut  aphis  dust)  without  adding  any 
water.  This  was  mixed  as  thoroughly  as  possible  with  a  garden 
rake,  allowed  to  dry  over  night  and  then  run  through  a  "Hunter 
Lightning  Sifter  and  Mixer,"  made  by  the  J.  H.  Day  Co.,  of  Cin- 
cinnati, Ohio.  In  this  machine  the  material  is  fed  into  the  hopper 
or  sifter,  where  it  comes  into  contact  with  stiff,  revolving  brushes 
sweeping  over  the  surface  of  a  semi-cylindrical  wire  screen.  This 
breaks  up  soft  lumps  and  reduces  the  mixture  to  the  fineness  of  the 
screen  or  finer.  From  the  sifter  the  material  drops  into  the  mixing 
box,  where  a  double-spiral  agitator  does  the  work  of  mixing  in  a  very 
short  time.  By  starting  with  pulverized  kaolin  and  using  no  moisture 
except  that  contained  in  the  ' '  Black  Leaf  40, ' '  the  lumps  formed  were 
very  soft  and  easily  broken  by  using  a  heavy  wire,  45  mesh  screen  in 
the  sifter.  Equipment  and  facilities  for  this  work  were  furnished 
by  the  Germain  Seed  and  Plant  Co.  of  Los  Angeles  and  part  of  the 
expense  was  borne  by  the  California  Walnut  Growers '  Association. 

Preparatory  to  the  season  of  1919  the  work  was  located  at  Goleta, 
Santa  Barbara  County,  California,  where  a  number  of  growers  had 
provided  themselves  with  power  dusters,  and  a  mixing  plant  was  set 
up  in  the  packing  house  of  the  Santa  Barbara  County  Walnut 
Growers'  Association.  This  plant,  after  considerable  experimenta- 
tion, was  arranged  as  follows:  On  the  second  floor  of  the  building 
was  located  a  "Sifter  and  Mixer."  Just  over  this  was  suspended  a 
five-gallon  iron  tank  for  the  "Black  Leaf  40,"  with  a  %-inch  pipe 
running  down  and  opening  into  the  end  of  the  mixer.  Connected 
with  the  outlet  of  this  pipe  was  a  small  electrically  driver  blower 
fan.  In  mixing,  the  proper  amount  of  pulverized  kaolin  was  run  into 
the  mixer,  using  a  ^-inch  screen  in  the  sifter  simply  to  take  out 
foreign  matter.     The  right  amount  of  "Black  Leaf  40"  was  then 


*  It  should  be  clearly  understood  that  the  names  Nicodust  and  Nicosulphur 
or  Nicosulphurdust  do  not  belong  to  any  particular  brand  or  company  but  may 
be  used  to  describe  any  mixtures  of  the  general  nature  indicated. 


264  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

allowed  to  trickle  slowly  from  the  tank  down  through  the  pipe  and  the 
fan  blew  this  in  a  fine  spray  into  the  kaolin  while  the  mixer  screw  was 
turning.  Each  charge  was  allowed  to  mix  about  ten  minutes,  when 
the  kaolin  would  be  thoroughly  impregnated  with  the  nicotine  solu- 
tion, but  with  many  soft  lumps.  This  mixer  discharged  into  a  per- 
pendicular chute  leading  down  through  the  floor  into  a  "Duplex 
Sifter"  made  by  the  same  firm.  This  consists  of  a  tight  box  enclosing 
a  large,  cylindrical  frame  covered  with  wire  screen.  When  running 
this  cvlinder  revolves  in  one  direction  while  brushes  inside  turn  in 

it 

the  opposite  direction,  sweeping  over  the  inner  surface  of  the  screen, 
pushing  the  fine  material  through  and  breaking  soft  lumps.  The 
fineness  of  the  dust  produced  depends  upon  the  fineness  of  this  screen. 
The  finer  the  screen  the  less  dust  can  be  produced  in  a  given  time.  The 
speed  at  which  material  can  be  run  through  the  screen  is  very  greatly 
affected  by  its  moisture  content.  If  the  dust  is  quite  dry  it  will  run 
through  a  very  fine  screen  like  water,  while  a  moist,  sticky  mixture 
is  slow  and  troublesome.  Screens  varying  from  25  to  100  mesh  were 
used  in  this  outfit;  when  previously  pulverized  kaolin  was  used  a 
heavy  wire,  45  mesh  screen  gave  a  very  satisfactory  dust.  Another 
mixer  was  placed  below  the  "Duplex  Sifter"  to  catch  the  material 
and  mix  it  uniformly  after  breaking  up  the  lumps.  From  this  mixer 
the  finished  dust  was  drawn  off  into  sacks  or  other  containers. 

In  the  original  outfit  the  upper  mixer  was  equipped  with  a  steam 
jacket  and  connected  with  a  boiler,  in  order  to  dry  the  material  while 
mixing.  This  proved  troublesome  and  resulted  in  driving  off  a  good 
deal  of  the  nicotine.  The  idea  was  then  hit  upon  of  mixing  an  equal 
quantity  of  hydrated  lime  with  the  kaolin  for  the  purpose  of  absorb- 
ing the  excess  moisture.  The  kaolin  in  use  at  the  time  was  rather 
moist.  With  this  mixture  it  was  found  possible  to  make  workable 
dust  up  to  5  per  cent  "Black  Leaf  40"  without  drying.  Stronger 
mixtures  were  run  through  twice,  using  a  12  mesh  screen  in  the 
"Duplex"  the  first  time.  Mr.  Phil  Marble,  manager  of  the  Santa 
Barbara  County  Walnut  Growers'  Association,  deserves  much  credit 
for  this  plant. 

This  outfit  made  400  pounds  of  dust  at  a  charge  and  with  it  four 
men  were  able  to  mix,  sack  and  pile  one  ton  per  hour,  or  about  six 
to  seven  tons  per  eight-hour  day  over  a  considerable  period.  About 
400  tons  of  dust  was  made  at  Goleta  during  April,  May  and  June, 
1919,  requiring  the  use  of  nearly  ten  tons  of  "Black  Leaf  40." 

As  a  result  of  this  quite  successful  season  and  the  growing  demand 
for  nicotine  dust  for  a  variety  of  purposes,  the  directors  of  the  Califor- 
nia Walnut  Growers'  Association  formed  a  subsidiary  company,  the 


Bulletin  336]  NICOTINE  DUST  AS  AN  INSECTICIDE  265 

Walnut  Growers'  Spray  Manufacturing  Co.,  purchased  a  factory 
building  in  Los  Angeles  and  moved  the  business  to  that  city.  The 
new  mixing  plant  was  similar  in  principle  to  the  one  at  Goleta,  but  on 
a  larger  scale.  Mixers  holding  a  charge  of  1000  pounds  were  used 
and  various  devices  added  for  expediting  the  handling  of  the  material. 
In  this  plant  the  ' '  Black  Leaf  40 ' '  was  simply  poured  slowly  into  the 
filler  through  two  funnels  while  mixing  instead  of  being  blown  in. 
There  was  also  added  to  the  outfit  a  Williams  "Little  Giant"  mill  so 
that,  if  desired,  the  filler  could  be  ground  before  mixing,  thus  making 
it  possible  to  use  cruder  material. 

A  change  was  also  made  at  this  time  in  the  material  used  for  filler. 
In  looking  about  for  a  cheaper  substance  than  kaolin,  attention  was 
called  to  the  waste  lime  from  beet  sugar  mills,  which  is  abundant 
in  southern  California,  and  may  be  had  at  practically  the  cost  of 
handling.  This  material  is  composed  of  very  finely  divided  calcium 
carbonate,  with  a  varying  amount  of  moisture  and  organic  matter  from 
the  beet  juice.  As  the  available  lime  was  quite  wet,  sometimes  con- 
taining as  high  as  25  per  cent  moisture,  and  no  facilities  were  avail- 
able for  drying  it,  the  plan  was  adopted  of  drying  with  quick-lime. 
A  very  good  grade  of  lime  was  obtained  from  Colton,  Cal.,  where  it 
is  burned  in  a  rotary  kiln.  It  was  in  small  pieces,  rarely  over  an  inch 
in  diameter.  About  25  per  cent  of  this  lime  was  first  mixed  with  the 
wet  sugar  beet  lime  by  piling  it  in  layers  and  shoveling  over  once  or 
twice  on  the  floor.  This  mixture  became  extremely  hot  and  most  of 
the  quick-lime  crumbled  into  a  fairly  fine  condition.  A  large  pile  of 
this  mixture  was  always  kept  on  hand.  For  making  nicotine  dust 
the  well-dried  lime  mixture  was  run  through  the  Williams  mill,  con- 
veyed by  air  up  into  a  large  bin  and  thence  discharged  through  an 
automatic  feeder  into  the  mixer.  A  large  amount  of  material  was 
turned  out  in  1920  with  this  outfit  which  often  ran  continuously 
night  and  day  with  three  shifts  of  nine  men  each.  This  method  was 
gradually  changed  and  improved  until,  at  the  present  time  (July, 
1921)  the  whole  grinding  and  mixing  process  is  carried  on  in  a  large 
ball  mill,  all  the  ingredients  being  put  into  the  cylinder  and  then 
ground  and  mixed  for  the  desired  length  of  time.  Much  credit  in 
connection  with  this  plant  is  due  to  Mr.  W.  W.  Thomas. 

The  writer's  connection  with  the  Walnut  Growers'  Spray  Manu- 
facturing Company  ended  January  1,  1921. 

Several  other  companies  are  now  making  nicotine  dust,  using 
various  more  or  less  successful  but  still  largely  experimental  methods. 
One  uses  a  ball  mill ;  another  a  Raymond  mill,  while  still  another 
sprays  the  "Black  Leaf  40 "'in  a  very  fine  mist  into  the  filler  while 


266  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

turning  in  a  large  drum  so  that  no  lumps  are  formed.  All  have  had 
more  or  less  trouble  in  obtaining  the  desired  dryness,  fineness  and 
uniformity  of  the  dust  without  loss  of  nicotine. 

WHAT   ARE   THE    BEST    MATERIALS    FOR    NICOTINE    DUST 

As  nicotine  is  a  very  expensive  substance  and  comparatively  large 
amounts  are  required  in  these  mixtures,  the  main  object  to  be  kept 
in  mind  must  be  to  produce  the  most  powerful  dust  possible  with  the 
minimum  amount  of  nicotine.  The  toxic  strength  of  the  dust  is 
influenced  both  by  the  form  and  amount  of  nicotine  used  and  the 
nature  of  the  filler. 

How  the  dust  acts. — So  far  as  the  writer's  observations  go,  this 
dust  acts  entirely  as  a  fumigant,  the  insects  being  poisoned  by  the 
nicotine  vapor  given  off  by  the  particles  of  dust.*  Two  alternatives 
are  presented  in  utilizing  a  given  amount  of  nicotine.  1.  To  make 
the  dust  of  such  a  nature  that  the  nicotine  will  be  as  volatile  as  pos- 
sible and  the  maximum  amount  be  given  off  in  the  minimum  of  time. 
This  means,  of  course,  that  the  dust  will  lose  its  efficiency  very  soon 
after  application.  2.  To  make  the  nicotine  less  volatile,  so  that  the 
dust  will  act  more  slowly  but  for  a  longer  time.  All  of  our  experience 
goes  to  show  that  the  former  of  these  methods  is  by  far  the  better, 
namely,  to  make  the  dust  of  such  a  nature  that  the  nicotine  will  be 
just  as  volatile  and  quick-acting  as  possible,  even  though  its  efficiency 
is  thereby  very  short-lived. 

CONSIDERATION    OF    THE    FILLER 

Several  materials  have  been  tested  as  to  their  adaptability  for 
use  as  the  filler  or  carrier.  In  general  it  may  be  said  that  no  one 
substance  has  been  found  to  be  greatly  superior  or  indispensable  for 
this  purpose,  but  almost  any  cheap,  readily  available  material  which 
is  capable  of  being  reduced  to  an  impalpable,  " smoky"  dust,  fairly 
bulky  and  free  from  undesirable  effects,  may  be  used. 

CHEMICAL   NATURE   OF  THE    FILLER 

Effect  on  nicotine. — When  nicotine  sulphate  is  mixed  with  kaolin 
or  any  other  inert  material  the  nicotine  remains  in  the  form  of  nicotine 
sulphate.  When  hydrated  or  quick-lime  is  used,  however,  a  reaction 
takes  place,  forming  sulphate  of  lime  and  free  nicotine.  The  latter 
is  more  volatile  than  nicotine  sulphate  and  for  this  reason  dust  made 
with  quick-lime  or  hydrated  lime  is  more  powerful  for  the  same  amount 
of  "Black  Leaf  40"  than  that  made  with  pure  kaolin,  sugar  beet 
lime  or  any  other  inert  filler.     The  mixing  of  "Black  Leaf  40"  with 


*  See  also  Mclndoo.2 


Bulletin  336]  NICOTINE  DUST  AS  AN  INSECTICIDE  267 

lime  appears  to  have  a  further  effect  than  setting  free  the  nicotine 
from  nicotine  sulphate,  as  a  strong  odor  of  ammonia  is  produced. 
This  combined  vapor  of  nicotine  and  ammonia  is  excessively  power- 
ful and  toxic,  especially  the  most  volatile  portion  which  is  given  off 
when  the  reaction  first  takes  place.  As  a  rule  a  dust  containing  free 
nicotine  is  more  effective  than  one  with  nicotine  sulphate. 

Mention  should  further  be  made  of  an  effect  which  takes  place 
when  ' '  Black  Leaf  40, ' '  sulphur  and  hydrated  lime  are  mixed  together. 
In  this  case  a  decided  reaction  takes  place ;  the  mixture  becomes  very 
hot,  so  that  the  sulphur  melts  or  even  takes  fire.  This  heating  is 
prevented  by  enclosing  the  mixture  in  an  air-tight  container  or  by 
exposing  it  to  the  open  air  until  the  reaction  has  become  completed, 
although  in  the  latter  case  some  nicotine  is  lost.  This  nicotine-sulfur- 
lime  mixture  is  a  very  powerful  one  and  is  sometimes  worth  using, 
especially  when  pests  controllable  by  nicotine  and  others  controllable 
by  sulphur  are  both  present.  It  is  possible  that  a  sulphide  of  nicotine 
is  formed;  if  so,  it  seems  even  more  volatile  and  toxic  than  nicotine 
itself.  At  present,  however,  this  reaction  is  not  well  understood  and 
considerable  losses  have  occurred  through  the  heating  or  spontaneous 
combustion  of  this  particular  combination.  There  has  also  been  a 
good  deal  of  uncertainty  and  irregularity  in  the  final  nicotine  strength 
of  such  mixtures. 

Drying  effect  of  the  filler. — It  is  possible  to  use  in  the  filler  some 
materials  which  combine  chemically  with  water,  as  well  as  simply 
absorbing  it.  Quick-lime,  for  instance,  takes  up  a  large  amount  of 
moisture  in  slaking  or  hydrating.  This  is  a  great  advantage  in  making 
nicotine  dust.  The  disadvantage  of  quick-lime  is  the  heat  which  is 
produced  in  the  reaction,  causing  the  loss  of  some  of  the  nicotine. 
Plaster  (Plaster  of  Paris)  combines  with  a  considerable  amount  of 
water  without  producing  any  heat  and  has  value  in  the  filler  on  this 
account.  Many  other  substances  combine  chemically  with  water  and 
thus  act  as  driers. 

Irritating  or  burning  effect  of  the  filler. — Nothing  should  be  used 
in  the  filler  which  might  possibly  cause  injury  to  animal  or  vegetable 
life.  Hydrated  lime  is  somewhat  objectionable  on  account  of  its 
irritating  effect  on  the  skin. 

PHYSICAL    NATURE    OF   THE    FILLER 

Fineness. — The  more  finely  divided  the  filler  the  better  dust  it  will 
make.  It  will  blow  and  stick  better  and  thus  the  nicotine  will  be 
brought  more  closely  into  contact  with  the  insects.  Some  substances 
break  up  easily  into  the  desired  condition,  while  others  require  pro- 
longed grinding. 


268  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION 

Weight. — At  first  thought  a  light,  bulky  material  would  seem  the 
best  for  dusting,  but  this  is  only  partially  true.  To  some  extent  at 
least  a  fairly  heavy  material,  like  sulphur  or  gypsum,  is  desirable 
because  it  can  be  blown  into  thick  vegetation  with  more  force  and  more 
in  a  solid  mass  like  a  water  spray  than  a  very  light  material.  As  a 
rule,  a  lighter  filler  is  better  for  large  trees  like  walnuts,  especially 
with  insects  that  are  easily  killed,  while  with  small  trees  or  vegetables 
and  insects  that  must  be  hit  directly  with  a  considerable  amount  of 
dust,  a  heavier  filler  is  better. 

Dryness. — It  is  very  desirable  that  the  filler  be  as  dry  as  possible 
before  adding  the  nicotine,  as  this  will  make  it  unnecessary  to  dry 
the  mixture  afterward. 

Absorptiveness. — It  was  at  first  thought  advisable  to  use  as  a  filler 
the  most  absorptive  materials  in  order  to  take  up  the  greatest  possible 
amount  of  "Black  Leaf  40"  in  a  given  amount  of  filler.  Experience 
has  indicated,  however,  that  the  nicotine  is  more  freely  given  off  from 
materials  which  do  not  absorb  it  readily  and  that  fillers  of  the  latter 
class  therefore  produce  a  quicker  acting  dust,  which  seems  to  be 
the  best. 

MATERIALS   WHICH    HAVE    BEEN   TRIED 

Kaolin 
The  material  used  came  from  a  deposit  at  lone,  California,  owned 
by  the  Philadelphia  Quartz  Co.,  of  Berkeley,  Cal.,  where  it  occurs 
mixed  with  fine  silica  sand,  from  which  it  is  separated  with  water. 
It  is  a  white,  soft,  extremely  fine  substance,  of  rather  light  weight, 
quite  absorptive  of  moisture  and  drying  into  soft,  chalky,  easily  pul- 
verized lumps.  It  is  free  from  chemical  effects,  and  forms,  in  many 
respects,  the  best  filler  material  which  we  have  used. 

Hydrate©  Lime 

This  is  the  most  generally  available  material  which  can  be  used. 

Its  absorptive,  blowing  and  sticking  qualities  are  excellent.     It  reacts 

with  nicotine  sulphate,  forming  free  nicotine.    The  chief  objection  to 

hydrated  lime  is  the  irritating  effect  which  it  has  on  the  skin  and 

eyes  of  the  operator. 

Quick  Lime 

Finely  pulverized  quick  lime  is  a  powerful  drier,  as  already 
described  on  page  267. 

Lime  Carbonate 

This  is  available  in  various  forms,  such  as  air-slaked  lime,  refuse 
sugar  beet  lime  and  various  natural  deposits  of  a  chalky  nature. 
When  dried  and  finely  pulverized  such  materials  make  a  very  satis- 
factory filler.    They  have  no  effect  upon  nicotine  sulphate. 


Bulletin  336]  NICOTINE  DUST  AS  AN  INSECTICIDE  269 

Gypsum,  Plaster 

Calcium  sulphate  or  gypsum  occurs  abundantly  in  nature  in 
various  forms  and  from  it  a  variety  of  materials  called  by  the  general 
term  plaster  are  prepared  by  grinding  and  heating.  All  forms  of 
gypsum  and  plaster  are  heavier  and  not  so  dusty  as  kaolin  nor  as  some 
of  the  forms  of  lime  mentioned  above.  They  are  also  apt  to  be  coarser 
unless  reground.  The  various  building  plasters,  from  which  a  portion 
of  the  water  has  been  removed  by  heating,  act  as  driers  and  do  not 
produce  heat.  They  have  the  disadvantage  of  forming  hard  lumps  in 
drying.  None  of  the  materials  mentioned  in  this  paragraph  react  with 
nicotine  sulphate. 

Kieselguhr,  Diatomaceous  Earth 

This  is  an  extremely  light  and  absorptive  material  and  is  fre- 
quently suggested  as  an  ideal  filler  for  nicotine  dust.  In  practice, 
however,  we  have  had  no  success  with  it.  It  does  not  form  a  good 
dust,  but  tends  to  cling  together  in  flakes  and  particles.  Its  great 
absorptiveness  seems  to  be  a  disadvantage  rather  than  an  advantage, 
since  the  nicotine  is  not  given  up  freely  and  quickly,  as  is  most 
desirable. 

Talc 

Finely  pulverized  talcum  may  have  some  value  as  a  filler.  It  is 
heavy  and  more  expensive  than  the  materials  thus  far  discussed. 
When  thoroughly  pulverized  it  makes  a  very  good  dust  and  sticks 
well.    It  does  not  react  with  nicotine  sulphate. 

Sulphur 
Sulphur  is  frequently  added  to  nicotine  dust  on  account  of  its 
value  as  an  insecticide  or  fungicide,  rather  than  simply  as  a  mechan- 
ical carrier.  In  the  latter  capacity  it  is  heavy,  nonabsorptive  and 
rather  expensive.  The  experience  has  been  quite  general,  however, 
that  when  mixed  with  sulphur  a  given  amount  of  nicotine  is  more 
effective  against  insects  than  with  any  of  the  other  fillers  mentioned. 
Why  this  is  so  is  not  entirely  certain.  We  have  already  mentioned 
the  fact  that  when  "Black  Leaf  40,"  sulphur  and  lime  are  combined 
a  reaction  takes  place  which  may  result  in  a  more  toxic  form  of 
nicotine.  Even  when  no  lime  is  used,  however,  the  nicotine  seems 
to  have  an  increased  effect  with  sulphur.  This  may  be  due  to  the  fact 
that  the  sulphur,  being  a  poor  absorbent,  gives  off  the  nicotine  more 
rapidly  than  do  some  of  the  other  materials.  If  this  is  the  case  a 
cheaper  material  having  the  same  quality  may  be  found.  Only  the 
very  finest  grades  of  sulphur  should  be  used.  Sulphur  cannot  be 
used  on  certain  crops  in  California  in  hot  weather  without  danger 


270  UNIVERSITY  OF  CALIFORNIA — EXPERIMENT  STATION 

of  burning.  Cantaloupes,  strawberries  and  walnuts  are  particularly 
sensitive.  There  is  also  danger,  in  some  cases,  of  a  so-called  sulphur 
poisoning,  especially  on  apricots  and  sometimes  on  apples.  This  shows 
as  a  yellowing  of  the  foliage  and  stunting  of  the  fruit. 

Tobacco  Dust 
When  well  ground  this  is  a  very  absorptive  material  and  makes  a 
good  dust.  It  may  be  fortified  with  nicotine  by  adding  '  'Black  Leaf 
40,"  but  is  commonly  too  expensive  to  be  considered  simply  as  a 
carrier.  Tobacco  dust  acts  more  slowly  than  nicotine  dust  containing 
the  same  amount  of  nicotine. 

CONSIDERATION    OF    NICOTINE 

Pure  nicotine  is  an  oily  liquid  and  one  of  the  most  deadly  poisons 
known.  Chemically  it  is  a  weak  base,  uniting  with  acids  to  form  salts. 
It  is  therefore  possible  to  obtain  a  great  many  different  compounds 
of  nicotine  and  it  is  reasonable  to  suppose  that  some  of  these  may  be 
more  toxic  to  insects  than  others.  In  our  rather  brief  experiments, 
however,  we  have  found  nothing  which  seems  to  be  decidedly  superior 
to  nicotine  itself.  This  has  been  tested  by  using  the  commercial 
"Nicofume"  as  a  source  of  nicotine,  combining  this  in  the  theoretically 
proper  proportions  with  the  following  acids :  acetic,  boric,  carbolic, 
cresylic,  formic,  hydrochloric,  hydrocyanic,  hydrofluoric,  oleic,  salicylic, 
stearic  and  tartaric.  Of  these  compounds,  none  has  shown  positive 
superiority  over  nicotine  itself  and  only  one  has  shown  any  promise 
whatever.  This  is  the  oleate.  Nicotine  oleate,  made  as  described  by 
Moore3  and  made  into  a  dust  with  kaolin,  is  quite  toxic  and  yet  the 
most  lasting  of  any  of  the  compounds  tried.  The  writer  has  found 
such  a  dust  of  particular  value  as  an  ant  powder,  especially  against 
the  Argentine  ant,  which  is  extremely  susceptible  to  nicotine.  Nico- 
tine oleate  does  not  seem  to  be  broken  down  by  lime  as  is  the  case 
with  the  sulphate. 

USE   OF   POISONS    OTHER   THAN    NICOTINE 

The  question  is  frequently  raised  whether  some  other  substance, 
cheaper  or  more  powerful  than  nicotine,  may  not  be  found.  We  can 
only  say  that  this  has  not  yet  been  «done.  Experiments  have  been 
made  with  dusts  containing  the  following  as  the  active  ingredient: 
Sodium  cyanide,  chloride  of  lime,  kerosene,  gasoline,  benzine,  various 
crude  phenols  and  cresols,  sulphur  chloride,  carbon  tetrachloride, 
pyrethrum  and  other  miscellaneous  materials.  Pyrethrum  is  power- 
ful against  some  insects  but  too  expensive;  none  of  the  other  materials 
tried  showed  any  promise  as  compared  with  nicotine. 


Bulletin  336]  NICOTINE  DUST  AS  AN  INSECTICIDE  271 

ADDITION    OF    OTHER    SUBSTANCES    TO    NICOTINE 

While  nothing*  has  been  found  to  replace  nicotine  in  the  dust  there 
are  some  substances  which  seem  to  increase  its  effect  somewhat.  The 
addition  of  a  small  quantity  of  kerosene,  for  instance,  seems  to  give 
nicodust  a  distinctly  increased  effect,  although  a  plain  kerosene  dust 
without  any  nicotine  has  little  or  no  effect  upon  aphids.  About  5  per 
cent  of  kerosene  may  be  added  to  a  fairly  dry  dust  without  destroying 
its  dusting  qualities.  Increased  efficiency  is  also  obtained  by  adding 
"Dry  Lime  Sulphur"  or  any  similar  preparation.  No  injury  to  vege- 
tation has  thus  far  been  found  from  the  use  of  at  least  10  per  cent 
of  this  material.  A  very  powerful  dust  is  obtained  by  using  all  three, 
"Black  Leaf  40,"  kerosene  and  "Dry  Lime  Sulphur,"  mixed  with 
a  filler.  This  mixture,  like  that  with  sulphur,  is  likely  to  heat  under 
some  conditions  but  not  when  placed  in  a  tight  container. 

HOW    MAY    NICOTINE    DUST    BE    IMPROVED    AND    CHEAPENED? 

In  using  "Black  Leaf  40"  as  a  wet  spray  a  strength  of  1  part  to 
1000  of  water  (.1  per  cent)  is  considered  a  strong  mixture.  To  kill 
the  same  insects  with  the  dust  a  10  per  cent  "Black  Leaf  40"  dust 
is  often  required.  In  other  words,  in  particles  of  dust  and  water  of 
the  same  weight,  the  former  contains  100  times  as  much  nicotine  as 
the  latter.  Can  not  this  amount  be  reduced?  If  it  is  true  that  nico- 
tine in  a  liquid  spray  acts  upon  insects  as  a  fumigant,  just  as  it 
appears  to  do  in  the  dust  (see  Mclndoo2),  then  it  must  be  that  the 
insect  is  subjected  to  more  nicotine  vapor  from  the  wet  spray  than 
from  the  dust,  even  though  the  latter  actually  contains  a  hundred 
times  as  much.  If  this  is  the  essential  difference  it  is  probably  due 
to  the  more  intimate  contact  of  the  wet  spray,  the  fact  that  more  water 
than  dust  sticks  to  the  insect  and  that  the  nicotine  is  set  free  more 
quickly  and  completely  from  a  quickly  evaporating  film  of  water  than 
from  solid  dust  particles.  (It  is  true,  however,  that  the  amount  of 
spray  applied  per  acre  or  plant  is  much  greater  than  that  of  dust, 
thus  equalizing  somewhat  the  amount  of  nicotine  used.) 

Contact  of  the  dust  with  the  body  of  the  insect  depends  upon  its 
fineness,  its  quality  of  adhesiveness  (some  materials  sticking  better 
than  others  even  with  particles  of  the  same  size),  the  amount  of  dust 
used  per  tree  or  acre,  and  the  nature  of  the  body  surface  of  the  insect 
itself.  The  nature  of  the  dust  particles  can  be  controlled  to  a  con- 
siderable extent  by  the  choice  and  preparation  of  the  filler,  but  the 
covering  of  each  individual  insect  with  a  heavy  coating  of  dust  can- 
not always  be  insured  even  with  a  heavy  application  of  a  very  fine 
and  adhesive  material,  since  most  of  the  problems  generally  handed 


262  UNIVERSITY  OF   CALIFORNIA EXPERIMENT  STATION 

over  to  dusting  are  those  where  for  some  reason  the  insects  are  hard 
to  reach,  as  in  the  case  of  tall  trees,  curled  leaves,  or  the  under  side 
of  leaves,  close  to  the  ground  where  a  direct  hit  is  impossible.  Since 
dust  preparations  have  been  on  the  market,  it  has  been  very  notice- 
able that  the  preference  of  the  public  is  for  the  stronger  mixtures, 
even  at  a  much  higher  price,  on  account  of  the  fewer  applications  and 
smaller  quantities  required.  These  stronger  mixtures,  like  that  con- 
taining 10  per  cent  "Black  Leaf  40,"  are  more  effective  because  it  is 
inevitable  that  many  of  the  insects  receive  few  or  no  dust  particles  and 
it  is  therefore  necessary  that  the  whole  atmosphere  about  them  be 
charged  as  heavily  as  possible  with  nicotine  vapor.  This  has  been 
accomplished  thus  far  by  using,  in  difficult  cases,  an  extravagant 
amount  of  nicotine  in  the  dust.  It  would  then  appear  that  the  greatest 
possibility  of  reducing  the  amount  of  nicotine  lies  along  the  line  of 
making  it  as  quickly  volatile  as  possible. 

TEMPERATURE 

The  success  of  nicotine  dusting  is  greatly  affected  by  tempera- 
ture ;  the  hotter  the  weather  the  greater  the  effect  produced  by  a  given 
strength  of  dust,  showing  again  that  the  effect  is  one  of  fumigation 
and  depends  upon  a  rapid  giving  off  of  nicotine  vapor.  This  is  more 
affected  by  temperature  than  by  any  of  the  other  factors  which  have 
been  discussed. 

POSSIBILITY    OF    REDUCING    COST    OF    MANUFACTURE 

The  present  prices  of  nicotine  dust  may  be  reduced  somewhat  by 
economies  in  the  process  of  manufacturing  and  distribution,  but  it  is 
evident  that  so  long  as  it  is  necessary  to  use  any  such  quantity  as 
10  per  cent,  or  even  5  per  cent,  of  a  high-priced  finished  product  like 
"Black  Leaf  40,"  subject  this  to  manufacturing  and  distribution 
costs  and  pay  transportation  charges  on  mixtures  containing  95  per 
cent  or  more  of  inert  material,  the  consumer's  price  of  the  finished 
mixtures  must  always  be  high. 

SUGGESTION    OF    A    NEW    TYPE    OF    DUSTING    MACHINE 

In  conjunction  with  Mr.  W.  W.  Thomas  the  writer  has  developed 
somewhat  the  idea  of  a  combined  dusting  and  mixing  machine,  the 
plan  being  to  place  the  raw  materials  in  the  machine  in  the  field  and 
do  the  mixing  in  the  hopper  of  the  dusting  machine,  just  as  is  done 
in  the  tank  of  a  liquid  sprayer.  Such  a  machine,  if  feasible,  would 
have  the  following  advantages :  The  grower  could  buy  materials  like 
' '  Black  Leaf  40, ' '  hydrated  lime  and  sulphur  almost  as  cheaply  as  the 


Bulletin  336]  NICOTINE  DUST  AS  AN  INSECTICIDE  273 

present  dust  manufacturers  and  save  the  expense  of  mixing,  con- 
tainers, "overhead,'1  several  profits,  and  much  of  the  freight.  He 
could  vary  the  strength  of  the  mixture  according  to  his  needs.  Little 
or  no  nicotine  would  be  lost  in  the  process  of  mixing  and  handling. 
The  first  full  strength  of  the  nicotine  and  ammonia  when  set  free  from 
"Black  Leaf  40 ':  by  lime  would  be  utilized.  By  adding  a  small 
amount  of  quick-lime,  or  other  material,  heat  could  be  developed  in 
the  mixture  and  the  dust  discharged  in  such  a  hot  condition  that  the 
nicotine  would  be  very  volatile  and  active,  and  a  smaller  amount  of 
"Black  Leaf  40"  would  therefore  be  required.  This  is  perhaps  the 
greatest  advantage  of  all  in  the  use  of  this  method. 

The  idea  of  the  machine  which  we  have  had  in  mind  contemplates 
a  hopper  containing  a  mixing  screw  into  which  finely  pulverized  and 
liquid  materials  would  be  placed  in  the  proper  proportions.  Hydrated 
lime  would  be  the  most  generally  available  filler  material,  with  ' '  Black 
Leaf  40"  as  a  source  of  nicotine.  Pulverized  quick  lime  or  "Dry 
Lime  Sulphur"  could  be  added  if  necessary  for  drying,  or  for  pro- 
ducing heat.  From  the  hopper,  after  brief  mixing,  the  material  would 
be  drawn  through  the  fan  (using  an  exhauster)  rather  than  blowing 
it  out  ahead  of  the  fan  as  in  the  present  machines.  The  action  of  the 
fan  would  complete  the  mixing  and  break  up  the  nicotine  lumps.  This 
would,  of  course,  be  a  power  machine ;  for  hand  use,  ready-made 
mixtures  would  still  be  required. 

USES    OF    NICOTINE    DUST 

Without  attempting  extensively  to  discuss  at  this  time  the  use  of 
nicotine  dust  in  the  control  of  specific  insects,  the  following  species 
may  be  mentioned  as  having  been  experimented  upon  with  at  least 
promising  results:  Walnut  Aphis  (Chromaphis  juglandicola  Kalt.), 
Rose  Aphis  (Macrosiphiim  rosea  Linn.),  Pea  Aphis  (Macrosiphum 
Pisi  Kalt.),  Melon  Aphis  {Aphis  gossypii  Glover),  Black  Citrus  Aphis 
(Toxoptera  aurantiae  Koch),  Bean  Aphis  (Aphis  rumicis  Linn.),  Cab- 
bage Aphis  (Aphis  brassicae  Linn.),  Rosy  Apple  Aphis  (Aphis  mali- 
foliae  Fitch),  Citrus  Thrips  (Scirtothrips  citri  Moulton),  Onion 
Thrips  (Thrips  t abaci  Lindeman),  Pear  Thrips  (Taeniothrips  pyri 
Daniel),  Beet  Hopper  (Eutettix  tenella  Baker,  Vine  Hopper  (Ery- 
throneura  comes  Say),  Squash  Bug  (Anasa  tristis  De  Geer),  Cucum- 
ber Beetle  (Diabrotica  spp.),  Cabbage  Worm  (Pontia  rapae  Lmn.)j 
Tent  Caterpillars  (Malacosoma  spp.),  Brown  Day  Moth  (Pseudohazis 
eglanterina  Boisd.),  Fall  Webworm  (Hyphantria  cunea  Drury),  Chal- 
cedon  Butterfly  (Lemonias  chalcedon  D.  &  H.),  Thistle  Butterfly 
(Vanessa   cardui   Linn.),   West   Coast   Lady   Bug    (Vanessa   caryae 


274  UNIVERSITY  OP  CALIFORNIA EXPERIMENT  STATION 

Hubn.),  False  Chinch  Bug   (Ny silts  ericae  Schilling  and  the  small 
variety  mimitus  Uhler). 

These  insects  show  a  great  difference  in  their  susceptibilty  to  nico- 
tine, the  range  being  from  a  1  per  cent  "Black  Leaf  40"  dust,  which 
gives  very  good  control  of  the  walnut  aphis,  to  the  10  per  cent  mixture 
which  is  required  satisfactorily  to  control  some  of  the  more  resistant 
species.  Essig3, 4  and  Campbell5  have  been  the  principal  experi- 
menters along  this  line. 

COMBINATIONS 

Nicotine  dust  may  be  mixed  with  sulphur,  lead  arsenate,  dry,  pul- 
verized Bordeaux  Mixture,  and,  in  fact,  with  any  dry  fungicide  or 
insecticide  for  the  control  of  more  than  one  pest  at  one  application. 

ACKNOWLEDGMENTS 

The  results  described  in  this  publication  have  not  been  obtained 
without  the  assistance  of  many  helpful  suggestions  and  various  forms 
of  aid  from  others.  Particular  credit  is  due  to  the  following :  Mr.  F.  A. 
Frazier,  of  Berkeley,  representative  of  the  Niagara  Sprayer  Company 
of  Middletown,  N.  Y. ;  Mr.  Carlyle  Thorpe,  manager  of  the  California 
Walnut  Growers'  Association,  Mr.  W.  W.  Thomas,  formerly  of  the 
Walnut  Growers '  Spray  Manufacturing  Co. ;  Mr.  Phil  Marble, 
manager  of  the  Santa  Barbara  County  Walnut  Growers'  Association, 
Mr.  J.  S.  Davis,  President  of  the  California  Sprayer  Company,  of 
Los  Angeles,  and  Mr.  E.  S.  Kellogg,  County  Horticultural  Commis- 
sioner of  Santa  Barbara. 

LITERATURE 

i  Smith,  Ralph  E. 

1918.  Dust  Spraying  Proves  Sure  Killer  of  Walnut  Aphis.  In  Diamond 
Brand  News  (Cal.  Walnut  Growers'  Assoc,  Los  Angeles,  Cal.), 
vol.  1,  pp.  4-5,  illus. 

2  McIndoo,  N.  E. 

1916.  Effects  of  Nicotine  as  an  Insecticide.  In  Jour.  Agr.  Research,  vol.  7, 
no.  3,  pp.  89-122,  pis.  1-3. 

3  Moore,  Wm. 

1918.  A  New  Fungicide  of  Economic  Importance.  In  Journal  of  Economic 
Entomology,  vol.  11,  p.  341. 

4  Essig,  E.  O. 

1920.  The  Pear  Thrips.     Cal.  Agr.  Exp.  Sta.  Circ.  223,  9  pp.,  illus. 

5  Essig,  E.  O.,  and  Horne,  W.  T. 

1921.  Plant  Disease  and  Pest  Control.     Cal.  Agr.  Exp.  Sta,  Circ.  227. 

e  Campbell,  Roy  E. 

1921.  Nicotine  Sulphate  in  a  Dust  Carrier  against  Truck  Crop  Insects. 
U.  S.  Dept.  Agr.  Circ.  154,  15  pp.,  illus. 


